What they found: That a “slavery effect” persists among white Southerners who currently live in the Cotton Belt where slavery and the plantation economy thrived from the late 18th century into the 20th century. Residents of those counties are much more likely today to express more negative attitudes toward blacks than their fellow Southerners who live in nearby areas that had few slaves; are more likely to identify as Republican; and are more likely to express opposition to policies like affirmative action, the study authors concluded.